linux-kernel - Re: [PATCH net-next v2 3/3] netlink: add validation of NLA_F

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Message-ID: <5f6c264c75f3ffe6c2cbcab2d174ad2c4c4c0bd6.camel@sipsolutions.net>
Date:   Tue, 23 Jul 2019 20:17:47 +0200
From:   Johannes Berg <johannes@...solutions.net>
To:     Stephen Hemminger <stephen@...workplumber.org>,
        Michal Kubecek <mkubecek@...e.cz>
Cc:     "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        David Ahern <dsahern@...il.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v2 3/3] netlink: add validation of NLA_F_NESTED
 flag

On Tue, 2019-07-23 at 11:02 -0700, Stephen Hemminger wrote:
> 
> There are some cases where netlink related to IPv4 does not send nested
> flag. You risk breaking older iproute2 and other tools being used on newer
> kernel. I.e this patch may break binary compatibility. Have you tried running
> with this on a very old distro (like Redhat Linux 9)?


There are *tons* of places where this (and other things) wasn't done
right, but the validation is only added for

 * all attributes on _new operations_ (that old userspace couldn't have
   been using since they're introduced after this patch)
 * _new attributes_ (dito, if the policy 'strict start' is filled)

johannes